Systems and methods of generating energy from solar radiation

ABSTRACT

A solar reflector assembly is provided for generating energy from solar radiation. The solar reflector assembly is configured to be deployed on a supporting body of liquid and to reflect solar radiation to a solar collector. A solar reflector assembly comprises an inflatable elongated tube having an upper portion formed at least partially of flexible material and a lower ballast portion formed at least partially of flexible material. A reflective sheet is coupled to a wall of the tube to reflect solar radiation. The elongated tube has an axis of rotation oriented generally parallel to a surface of a supporting body of liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 12/849,761, filed Aug. 3, 2010, which isincorporated by reference herein in its entirety, which is anon-provisional of and claims priority to U.S. patent application Ser.No. 61/231,081, filed Aug. 4, 2009, 61/233,667, filed Aug. 13, 2009, and61/244,349, filed Sep. 21, 2009, each of which is incorporated byreference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to solar energy systems.

BACKGROUND OF THE DISCLOSURE

There has been a long-standing need to provide energy generation fromrenewable sources. Various renewable energy sources have been pursued,such as solar energy, wind, geothermal, and biomass for biofuels as wellas others.

Solar radiation has long been a prime candidate for fulfilling thisneed. Various approaches have been taken to achieve energy generationfrom solar radiation. To that end, much focus has been directed tocreating a low cost solar energy conversion system that functions withhigh efficiency and requires little maintenance.

For example, solar panels formed of photovoltaic cells (solar cells) areused to transform light to electricity. Such systems have beenimplemented in various applications. Solar panels have been generallyeffective for small-scale electrical generation, such as powering smallelectronics, electrical generation for residential applications, andelectrical generation for space-based systems. However, current solarpanel technology has been ineffective for large-scale uses, such aselectrical generation sufficient for municipal applications. The costsassociated with such large-scale usages have been prohibitive. Currentsolar panels are relatively expensive and do not allow cost-effectiveenergy storage.

Other approaches include concentrating solar radiation on solarcollectors for energy generation, commonly referred to as concentratedsolar power (CSP). CSP systems typically use reflective surfaces toconcentrate the sun's energy from a large surface area on to a solarcollector. For example, the concentrated solar energy can be used toheat a working fluid. The heated fluid is then used to power a turbineto generate electricity. Alternatively, photovoltaic cells can be usedat the solar collector, eliminating the need for numerous, expensivecells. In an effort to maximize efficiency, the reflective surfaces ofCSP systems can be coupled to a device that tracks the sun's movement,maintaining a focus on a receiver target throughout the day. Using thisapproach, the CSP system can optimize the level of solar radiationdirected towards the solar collector.

Although such CSP systems are better than traditional flat-panelphotovoltaic cells for large-scale applications, shortfalls exist. Forexample, glass and metal reflector assemblies are expensive tomanufacture, ship and install. Further, current tracking devices usedwith CSP can be relatively expensive and complicated. As a result,current approaches have yet to achieve significant market penetrationbecause of cost issues.

Biomass production, such as algae and other microorganisms, hasincreasingly been of interest. The potential usage of such material isfound across a wide range of applications, including biofuel feedstockproduction, fertilizer, nutritional supplements, pollution control, andother uses.

Current approaches for biomass production include “closed-air” systemsthat contain biomass production within a controlled environment,limiting exposure to outside air. Examples of such systems includeclosed photo-bioreactor structures forming a closed container forhousing a culture medium for generating biomass. Having a controlledenvironment helps maximize the generation of algal material by limitingexposure to invasive species as well as controlling other environmentalfactors that promote algal growth. Closed-air systems significantlyreduce evaporation and therefore significantly reduce demands on waterresources. In addition, closed-air systems facilitate the sequestrationof carbon dioxide gas, which promotes algal growth, facilitiescompliance with environmental regulations, and, according to a largenumber of scientists, benefits the environment generally. However, suchsystems can be expensive and, in many instances, cost prohibitive.

It should be appreciated that there remains a need for a system andmethod of generating energy from solar radiation in a low-cost,large-scale manner. There also exists a need for a closed-airphoto-bioreactor to promote algal growth in a low-cost, large-scalemanner. The present disclosure fulfills these needs and others.

SUMMARY OF THE DISCLOSURE

In general terms, the present disclosure provides a solar reflectorassembly useable for generating energy from solar radiation. Embodimentsof the solar reflector assemblies are inflatable elongated tubes offlexible material with each tube including a reflective sheet to reflectsolar radiation to a solar collector. This structure and the materialsemployed provide significant cost savings for manufacture, shipping anddeployment of the solar reflector assemblies. The solar reflectorassembly is configured to be deployed on a supporting body of liquid.This provides both liquid ballasting capability and structural support.Beneficially, the solar reflector assemblies are inexpensive tomanufacture, deploy and operate, providing a cost effective solution forenergy generation.

Exemplary embodiments of a solar reflector assembly includes aninflatable elongated tube having an upper portion formed at leastpartially of a flexible material and a lower ballast portion formed atleast partially of a flexible material. The lower ballast portion maydefine a reservoir containing fluid facilitating ballast. The elongatedtube has an axis of rotation oriented generally parallel to a surface ofa supporting body of liquid and a reflective sheet coupled to a wall ofthe tube to reflect solar radiation towards the solar collector. Thereflective sheet may be coupled to either an interior wall or anexterior wall of the elongated tube. The fluid facilitating ballast hasa top surface that is generally parallel to a surface of a supportingbody of liquid.

In exemplary embodiments, the reflective sheet can be configured toreflect substantially all solar radiation towards the solar collector.In another exemplary embodiment, the reflective sheet can be configuredto substantially reflect a first prescribed wavelength range towards asolar collector and to substantially transmit a second prescribedwavelength range therethrough. In the case of an interior reflectivesheet, the reflective sheet may also facilitate equilibrium of pressureon its opposing sides. One end cap assembly may be coupled to theelongated tube, or a pair of end cap assemblies can be coupled to theelongated tube, in which at least one of the end cap assemblies isconfigured to facilitate the flow of gas and/or liquid into and out ofthe elongated tube to maintain pressure within the tube. The upperportion formed of thin-gauge, flexible material allows solar radiationto pass through for reflection by the reflective sheet.

Inflatable supports can be disposed on the exterior wall of the tube tomaintain the reflective sheet in a prescribed orientation. For example,the reflective sheet can be disposed to have various cross sectionalshapes, including flat, v-shaped, u-shaped, or parabolic, among others,as desired. A pair of supports can be used, coupled to longitudinalsides of the reflective sheet.

In a detailed aspect of an exemplary embodiment, the reflective sheet isformed as a hot mirror, configured to reflect infrared (IR) radiation(e.g., heat reflective) while allowing visible light to pass through(e.g., visibly transparent), across wide angles of incidence. Forexample, the reflective sheet allows transmittance of at least 50percent of incident energy in the wavelength band between about 400 nmand 700 nm at normal incidence. In a detailed aspect of an exemplaryembodiment, the reflective sheet allows transmittance of at least 90percent of incident energy in the wavelength band between about 400 nmand 700 nm at normal incidence.

In another detailed aspect of selected exemplary embodiments, thereflective sheet can have a high percentage of reflection forsubstantially all incident solar IR radiation above about 700 nm or, inother embodiments, above about 750 nm. In yet other embodiments, thereflective sheet can be configured to have a high percentage ofreflection within a bounded range of IR wavelengths. Exemplary rangesinclude 700-1200 nm, 700-2000 nm, 750-1200 nm, and 750-2000 nm, amongothers. It should be appreciated that other ranges can be used.

More particularly, by example and not limitation, a system forgenerating energy from solar radiation is provided, comprising a poolhousing a supporting body of liquid and one or more solar reflectorassemblies disposed on the supporting body of liquid. Each solarreflector assembly includes an inflatable elongated tube having an upperportion formed at least partially of flexible material, a lower ballastportion formed at least partially of flexible material and an axis ofrotation oriented generally parallel to a surface of the supporting bodyof liquid, and a reflective sheet coupled to a wall of the tube toreflect solar radiation towards a solar collector. The reflective sheetmay be coupled to an interior wall of the elongated tube such that theupper portion and the lower ballast portion are separated by thereflective sheet. Alternatively, the reflective sheet may be coupled toan exterior wall of the elongated tube.

The reflective sheet may be coupled to the elongated tube in a manner toprovide a pressure differential between opposing sides of the reflectivesheet such that the reflective sheet can be given a prescribed shape tofacilitate reflection of solar radiation towards the solar collector.The solar reflector assembly may facilitate equilibrium of pressure onopposing sides of the reflective sheet. The lower ballast portion of theelongated tube contains liquid facilitating ballast. The liquidfacilitating ballast has a top surface that is generally parallel to thesurface of the supporting body of liquid. The system further includes asolar collector positioned to receive reflected solar radiation from thereflective sheet.

Embodiments of the system for generating energy from solar radiation mayfurther comprise an electrical generator assembly operatively coupled tothe solar collector to convert the reflected solar radiation toelectricity. At least one end cap assembly can be coupled to anelongated tube, and a pair of end cap assemblies can be coupled toopposing ends of the one or more elongated tubes, in which at least oneof the end cap assemblies is configured to facilitate the flow of gasand/or liquid into and out of the elongated tube to maintain pressurewithin the tube. A rotation assembly may be coupled to an elongated tubeat any location on the tube. In exemplary embodiments, a rotationassembly is coupled to at least one of the end cap assemblies to inducecontrolled rotation of the elongated tubes to direct the reflected solarradiation to the solar collector.

In an exemplary embodiment, the reflective sheet is coupled to theelongated tube in a manner to provide a pressure differential betweenopposing sides of the reflective sheet such that the reflective sheetcan be given a prescribed shape to facilitate reflection of solarradiation towards the solar collector. Alternatively, the reflectivesheet can be configured to be taut when the elongated tube is inflatedto form a generally planar shape. In yet another embodiment, thereflective sheet can be configured to hang between spaced-apart portionsof the internal wall of the tube to form a generally catenary shape.

In an exemplary embodiment, the elongated tube defines an elongatedreservoir extending the length of the tube for passing a heat-transferfluid therethrough, the elongated reservoir positioned above thereflective sheet such that solar radiation reflected by the reflectivesheet is directed towards the elongated reservoir. The elongated tubecan further define a plurality of elongated reservoirs positioned abovethe reflective sheet, defining multiple focal areas of reflectedradiation present at different angles of incident solar radiation. Inthis manner, the solar collector can be coupled to the tube, throughwhich a heat-transfer fluid can pass to absorb the reflected radiation,and then be used to power electricity generation.

In exemplary embodiments, the solar reflector assembly may comprise oneor more pass-through fittings coupled to the elongated tube tofacilitate the flow of gas and liquid into and out of the elongatedtube.

In a detailed example of an exemplary embodiment, the solar reflectorassembly or system can include a rotation assembly coupled to at leastone end of the elongate tube and configured to rotate the elongated tubesuch that the reflective sheet directs solar radiation towards the solarcollector throughout the day. In one approach, the rotation assembly caninclude a plurality of gas bladders coupled to the elongated tube, inwhich the rotation assembly is configured to adjust the content of gasbladders to rotate the elongated tube. In another approach, the rotationassembly is coupled to at least one end of the elongated tube to inducecontrolled rotation of the elongated tube to direct the reflected solarradiation towards the solar collector.

In another exemplary embodiment, a plurality of elongated tubes arecoupled together along longitudinal sides, forming a raft, in which areflective sheet is disposed either within or atop each tube. The tubescan further include one or more reservoirs for passing heat-transferfluid through. Alternatively, an external solar collector can bedisposed in a prescribed location, spaced apart from an elongated tubeor from the raft of elongated tubes to receive reflected solar radiationfrom the reflective sheets.

The elongated tube may further comprise a culture medium forphotosynthetic biomass, thus forming a combined solar reflector andphotobioreactor assembly (“CSP/PBR”). The culture medium housed in thetube can be used, e.g., to facilitate photosynthetic biomass growth,such as algal biomass. The reflective sheet may be configured tosubstantially reflect a first prescribed wavelength range towards asolar collector and to substantially transmit a second prescribedwavelength range therethrough to the culture medium within the elongatedtube. In this manner, a portion of solar energy is directed towards thesolar collector, while another portion is utilized by the culturemedium, e.g., to facilitate photosynthetic biomass growth, such as algalbiomass. The CSP/PBR assemblies may be disposed on a supporting body ofliquid and include a solar collector positioned to receive reflectedsolar radiation from the reflective sheet. Beneficially, this embodimentserves to reduce the heat input, and therefore the cooling load for thebiomass production component of such an embodiment.

For purposes of summarizing the disclosure and the advantages achievedover the prior art, certain advantages of the disclosure have beendescribed herein. Of course, it is to be understood that not necessarilyall such advantages may be achieved in accordance with any particularembodiment of the disclosure. Thus, for example, those skilled in theart will recognize that the disclosure may be embodied or carried out ina manner that achieves or optimizes one advantage or group of advantagesas taught herein without necessarily achieving other advantages as maybe taught or suggested herein.

All of these embodiments are intended to be within the scope of thedisclosure herein disclosed. These and other embodiments of the presentdisclosure will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the disclosure not being limited toany particular preferred embodiment disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the following drawings in which:

FIG. 1 is cross-sectional view of an embodiment of a solar energycollection system in accordance with the present disclosure;

FIG. 2 is a perspective view of an embodiment of an array of solarreflector assemblies of a solar energy collection system in accordancewith the present disclosure;

FIG. 3 is a perspective view of an embodiment of an end cap assemblycoupled to a solar reflector assembly in accordance with the presentdisclosure;

FIG. 4 is a cross-sectional view of an embodiment of a solar energycollection system in accordance with the present disclosure;

FIG. 5 is a cross-sectional, perspective view of an embodiment of anarray of solar reflector assemblies in accordance with the presentdisclosure;

FIG. 6 is a cross-sectional view of an embodiment of an array of solarreflector assemblies in accordance with the present disclosure;

FIGS. 7 a-c are cross-sectional views of an embodiment of a solarreflector assembly in accordance the present disclosure;

FIGS. 8 a-c are cross-sectional views of embodiments of solar reflectorassemblies in accordance with the present disclosure;

FIGS. 9 a-b are cross-sectional views of embodiments of solar reflectorassemblies in accordance with the present disclosure;

FIG. 10 is a cross-sectional view of an embodiment of a solar reflectorassembly in accordance with the present disclosure;

FIG. 11 is a perspective view of an embodiment of a solar reflectorassembly in accordance with the present disclosure;

FIG. 12 is a cross-sectional view of an embodiment of a solar reflectorassembly having an external reflector in accordance with the presentdisclosure;

FIG. 13 is a cross-sectional view of an embodiment of a solar reflectorassembly having an external reflector in accordance with the presentdisclosure;

FIG. 14 is a cross-sectional view of an embodiment of a solar reflectorassembly having an external reflector in accordance with the presentdisclosure;

FIG. 15 is an embodiment of a solar energy collection system inaccordance with the present disclosure;

FIG. 16 is a cross-sectional view of a solar energy collection system inaccordance with the present disclosure;

FIG. 17 is a cross-sectional view of an embodiment of a concentratedsolar power/photobioreactor assembly in accordance with the presentdisclosure;

FIG. 18 is a perspective view of an embodiment of an array ofconcentrated solar power/photobioreactor assemblies in accordance withthe present disclosure;

FIG. 19 a is a perspective view of an embodiment of an end cap assemblycoupled to a concentrated solar power/photobioreactor assembly inaccordance with the present disclosure;

FIG. 19 b is a perspective view of an embodiment of an end cap assemblyhaving pass-throughs and coupled to a concentrated solarpower/photobioreactor assembly in accordance with the presentdisclosure;

FIG. 20 is a graph depicting percent transmittance at zero degreesincidence, as a function of wavelength, for an exemplary embodiment of areflective sheet for a reflector/photobioreactor assembly in accordancewith the present disclosure;

FIG. 21 is a cross-sectional view of an embodiment of a solar reflectorassembly in accordance with the present disclosure;

FIG. 22 is a cross-sectional view of an embodiment of a solar reflectorassembly in accordance with the present disclosure;

FIG. 23 is a perspective view of an embodiment of an array of solarreflector assemblies of a solar energy collection system in accordancewith the present disclosure;

FIG. 24 is a perspective view of an embodiment of an array of solarreflector assemblies of a solar energy collection system in accordancewith the present disclosure;

FIG. 25 is a cross-sectional view of an embodiment of a solar reflectorassembly in accordance with the present disclosure;

FIG. 26 is a perspective view of an embodiment of an array of solarreflector assemblies of a solar energy collection system in accordancewith the present disclosure;

FIG. 27 a is a perspective view of an embodiment of a solar reflectorassembly in accordance with the present disclosure; and

FIG. 27 b view of an embodiment of a solar reflector assembly havingpass-throughs in accordance with the present disclosure.

DETAILED DESCRIPTION

With reference now to the drawings, and particularly FIGS. 1 and 2,there is shown an array 1 of solar reflector assemblies 10. Each solarreflector includes an inflated elongated tube 12 having a reflectivesheet 14 coupled along opposed sides of the sheet to a wall of the tube.In exemplary embodiments, reflective sheet 14 is coupled to an interiorwall 15 of the elongated tube 12 so that the reflective sheet 14 dividesthe elongated tube 12 into two portions, an upper portion or chamber 21and a lower ballast portion or chamber 23.

More particularly, in exemplary embodiments the elongated tube 12 is aunitary structure that includes lower ballast portion 23, which providesballast for the solar reflector assembly 10. In other words, lowerballast portion 23 is the lower section of the elongated tube itselfand, as such, is integrally formed with the elongated tube 12. Thisstructure is advantageous because it obviates the need for additionalcomponents or structural elements to facilitate ballast. It also enablespressure differential or pressure equilibrium between the chambers 21,23 on either side of the reflective sheet 14, as described in moredetail herein. The elongated tubes may include a gas in the upperchamber 21 and a reservoir liquid 20 in the lower chamber 23 tofacilitate ballast. As discussed in more detail herein, the reflectivesheet could also be coupled to an exterior wall of the tube.

The solar reflectors are supported by a body of liquid 16 and areconfigured to rotate to direct reflected solar radiation towards a solarcollector 18. The solar reflectors are used to reflect solar radiationtowards a solar collector 18 configured to transform the solar energy toelectricity or process heat. Beneficially, the solar reflectorassemblies are inexpensive to manufacture and operate, providing a costeffective solution for electrical generation or process heat from solarenergy.

Each tube 12 is formed of transparent, lightweight flexible plasticoptionally coupled at each end to rigid end cap assemblies 24, whichfacilitate the flow of liquid and gas into and out of the tubes.Positive pressure within the tube keeps them rigid and maintains thetube in a generally cylindrical configuration having a substantiallyconstant cross section along the length of the tube. The tube is set onan expanse of liquid 16 in a pool 19 and includes a reservoir of fluid20 to facilitate ballast of the tube and maintain buoyancy in aprescribed manner to best track the sun, as described herein. The tubes12 will float at a level such that the liquid level within the tube isgenerally even or parallel with the level of liquid 16 on which the tubeis floating. More specifically, in operation the top surface of theballast liquid is substantially parallel to the top surface of thesupporting body of liquid. However, the level of liquid within the tubecan vary, from empty to full with liquid, as desired.

The tubes 12 are configured in an elongated cylindrical configuration.In exemplary embodiments, the tubes are formed of a single sheet of athin gauge, flexible material, which can be various plastics such aspolyethylene, having a thickness between about 50 microns (2 mil) and300 microns (12 mil). In other embodiments, tubes can be formed ofmultiple layers and multiple sections of material. In addition, otherlightweight, flexible materials or combinations of materials can beused. Tubes of various sizes can be used, to include tube diameter andtube length, without departing from the disclosure. In the presentembodiment, the entire tube is formed of transparent material; however,it is sufficient if an upper portion of the tube is transparent toenable solar radiation to be directed towards the reflective sheet.

The tubes can be susceptible to deterioration over time as result ofexposure to solar radiation. For example, polyethylene can besusceptible to UV-B radiation, and other materials may be susceptible toother ranges of radiation. The tubes can be protected from prematuredeterioration using systems and methods as disclosed in the presentinventor's co-pending application, U.S. appl. Ser. No. 12/253,962, filedOct. 18, 2008, entitled “System and Method for Protecting Enclosure fromSolar Radiation,” which is incorporated by reference herein for allpurposes.

With reference now to FIG. 2, the reflective sheet 14 is disposed withinthe elongated tube 12, having opposing longitudinal sides attached tothe interior wall of the tube. The reflective sheet is formed oflightweight flexible reflective material, such as PET polyester filmsold under the brand name Mylar®, available from E. I. Du Pont DeNemours & Co. Other examples of usable materials include reflectivepolyester film, metalized polymer film, metallic film, or other materialhaving sufficient reflective traits while being sufficientlylightweight. In the exemplary embodiment, the reflective sheet is formedof one layer of material configured to reflect a broad wavelengthspectrum. In other embodiments, the substrate film is also a polymersheet with a reflective sheet laminated, adhesively applied, orotherwise disposed on top. In addition, multiple layers can be used, andthe reflective sheet can be configured to allow prescribed wavelengthsof solar radiation to pass through, while reflecting other wavelengthsof solar radiation towards the solar collector.

The reflective sheet 14 can be coupled to the elongated tube 12 toenable a pressure differential to be maintained on opposing sides of thesheet. The pressure differential can be used to form the reflectivesheet to a prescribed shape. For example, a higher pressure can bemaintained on the upper surface of the reflective sheet such that thereflective sheet has a curved or, more preferably, a generally parabolicshape. Alternatively, the solar reflector assembly can be configured tomaintain pressure equilibrium on both sides of the reflective sheet tofacilitate other desired shapes for the reflective sheet. For example,the one or more end caps can be configured to allow gas to move betweenthe upper portion and lower ballast portion of the tubes by coupling apass-through to the upper chamber with a pass-through to the lowerchamber. As discussed in more detail below, the reflective sheet can beconfigured to assume any number of different shapes without departingfrom the disclosure.

In an exemplary method of manufacture, a sheet of reflective material isattached along longitudinal side edges to a first side of a sheet oftube material at a prescribed distance from each other. Opposinglongitudinal side edges of the tube material are attached to each otherforming a cylinder with the reflective material disposed within theinterior of the tube. The distance between the edges of the reflectivematerial is selected to form a prescribed shape for the reflectivesheet, when in use.

With reference again to FIGS. 2 and 3, end cap assemblies 24 aredisposed at opposing ends of the tube 12, and a rotation assembly 26 isconfigured to enable rotation of the tubes about a longitudinal axisoriented generally parallel to the surface of the supporting body ofliquid 16. Rotation assembly 26 includes a motor 28 and a transmissionsystem 30. The motor 28 is connected to at least one end cap assembly 24by the transmission system 30. The motor 28 provides power to turn thetube 12 either way. It is possible to drive both ends of the tube 12 byinstalling motors and transmission systems at both ends. The tubes canbe turned to track the sun to optimize reflection of solar radiationonto the solar collector. In other embodiments, longitudinal bladderscan be built into the tubing material or otherwise used to support thetubes. Air pressure varied within said bladders can be used to changethe buoyancy of one side of the tube, causing rotation until equilibriumis reached.

Each end cap assembly 24 is configured to facilitate flow of gas andliquid to and from the interior of the elongated tube 12. To that end,end cap assembly 26 may include liquid transfer tubes 32 and gastransfer tubes 34 that extend from the end caps. Liquid can be injectedor withdrawn through liquid transfer tubes to regulate how high theelongated tubes 12 float in the support liquid 16. Similarly, gas can beinjected or withdrawn through gas transfer tubes. The inlets and outletspass through pipes 36, which also serve as axles on which end-capsrotate. By passing through the axis of rotation of the end-caps, theliquid and gas transfer tubes can thus be permanently interfaced to theelongated tube 12 and can allow fluid and gas transfer while theelongated tube is turning. However, other inlets and outlets passingthrough both, eccentrically mounted control valves on the end-cap, orvalves mounted on the plastic tubing itself are possible in otherembodiments without departing from this disclosure.

In exemplary embodiments, the liquid transfer tubes 32 are submergedwithin the liquid 20 within the tube. Gas transfer tubes 34 are disposedabove the liquid. In other embodiments, various other configurations canbe used. One liquid and one gas transfer tube passing through eachend-cap are used. It is also possible to have more than two transfertubes passing through each end-cap. In exemplary embodiments, therotation element includes sealed ball bearings, which enable long lifeof the assembly despite potential prolonged exposure to moisture. Thereare multiple methods possible for sealing the ends of the tubes.

The solar energy collection system can include an array of solarreflector assemblies configured to reflect solar radiation towardsmultiple solar collectors. For example, the system can include groupingsof solar reflectors disposed on opposing sides of linear solarcollectors, and the solar reflectors can be directed to the closestsolar collector.

With reference now to FIGS. 4 and 5, a solar reflector assembly 110 isshown having a heat-transfer reservoir 142 positioned above a reflectivesheet 114 such that solar radiation reflected by the sheet is directedtowards the reservoir. More particularly, the reservoir is in an upperportion of the elongated tube 112, extending the entire length of thetube. Heat-transfer fluid enters a heat-transfer reservoir 142 at afirst end cap, and it absorbs the reflected solar radiation from thereflective sheet 114 of the solar reflector assembly 110 as it passesthrough the heat-transfer reservoir 142 to a second end cap assembly.The heated fluid is then directed to power an electrical generator (notshown) or is used for process heat. Reflective sheet 114 is coupled toan interior wall of the elongated tube 112 so that the reflective sheet114 divides the elongated tube 112 into two portions, an upper portionor chamber 121 and a lower ballast portion or chamber 123. An array ofsolar reflectors 110 can be configured to rotate to track the sun toensure that the reflective solar radiation is directed towards thereservoir, as in FIG. 5. The solar reflector assemblies 110 aresupported by a body of liquid 116 in a pool 119.

In exemplary embodiments, the heat-transfer reservoir 142 is attached toor formed in the wall of the elongated tube from the same polymermaterial. For example, an exterior and an interior sheet of polymermaterial can be used together by spaced apart, generally parallel seamsto form the heat-transfer reservoir. The material for the heat-transferreservoir should have sufficient strength and durability characteristicsto handle the anticipated pressure, heat, and so on, when theheat-transfer fluid is heated.

In other embodiments, the heat-transfer reservoir can include additionalstructure and/or other materials, to facilitate the use of selectedheat-transfer fluids that achieve high pressures and high temperatures.For example, the heat-transfer reservoir as discussed above can furtherinclude a rigid tube installed at tube deployment, sandwiched betweenthe exterior and interior sheets and extending between the end capassemblies.

With reference now to FIGS. 6 and 7 a-c, an array 200 of solar reflectorassemblies 210 is shown. Each solar reflector assembly 210 includes atube 212 having a plurality of heat-transfer reservoirs 242 a-c, similarto the heat-transfer reservoir depicted in FIG. 4. A reflective sheet214 is disposed within each tube 212. The elongated tubes 212 arecoupled together along longitudinal sides 270, forming a raft. A raftconfiguration can be used in other embodiments, such as with an externalsolar collector that can be disposed in a prescribed location, spacedapart from the raft to receive reflected solar radiation from thereflective sheets.

Use of a plurality of heat transfer reservoirs can be effective inembodiments in which the solar reflector assembly does not rotate totrack the sun. Rather, as the sun progresses across the sky, thereflected focal area of the reflective sheet will track across theplurality of heat transfer reservoirs. The system can be configured topass the heat-transfer fluid through the appropriate reservoir atprescribed times to coincide with the location of the reflected focalarea.

For example, as shown in FIG. 7 a, the system passes heat-transfer fluidthrough the first reservoir 242 a in the morning. During midday, thesystem passes heat transfer fluid through the center reservoir 242 b(FIG. 7 b). In the afternoon, the system passes heat transfer fluidthrough the third reservoir 242 c (FIG. 7 c). In other embodiments, thesystem can be designed with any number of heat-transfer reservoirs, andthe size and configuration of each reservoir of the plurality ofreservoirs can vary from each other, as requirements dictate.

With reference now to FIGS. 8 a-c, the reflective sheet 14 can beconfigured to achieve various different shapes. For example, as in FIG.8 a, the reflective sheet 14 can be configured to be held taut when thetube is inflated, forming a generally planar shape. Alternatively, as inFIGS. 8 b, c, a curved shape for the reflective sheet 14 a, 14 b canalso be used. The reflective sheet 14 a can be configured to drapebetween the attachment seams of the opposing longitudinal edges of thereflective sheet, forming a generally catenary shape (FIG. 8 b).Alternatively, as in FIG. 8 c, the curved shape can be formed bymaintaining a pressure differential on opposing sides of the sheet 14 b,forming a generally parabolic shape. Nonetheless, other shapes for thereflective sheet can be used without departing from the disclosure.

With reference now to FIGS. 9 a-b, the elongated tube 312 of the solarreflector assembly 310 can be configured to achieve various differentcross-sectional shapes. In each example depicted, the tube 312 has agenerally constant cross-section profile. In other embodiments, thecross-section profile can vary across the length of the tube. FIG. 9 adepicts an elongated tube 312 having an oval shaped cross section, usedwith a curved reflective sheet 314 a. FIG. 9 b depicts an elongated tube312 having an oval shaped cross section, used with a planar reflectivesheet 314 b. It should be appreciated that variations of these shapesand others having different parameters can be used. In addition, othercross-sectional shapes for the tube can be used, such as an ellipse,superellipse, vesica piscis, lens, and polygon, to name a few, withoutdeparting from the disclosure.

Various approaches for manufacture can be used. For example, the tubecan be formed by an upper panel and a lower panel, along opposing seams,and the reflective material is disposed therebetween attached at theseam. The tube can also be formed by a single sheet of material to whichthe reflective sheet is attached. The opposing ends of the sheet can becoupled together forming the tube, having the reflective sheet disposedin the interior. Due to the flexibility of the material it can be rolledup into a compact format for shipping and deployment.

With reference now to FIGS. 10 and 11, a solar reflector assembly 410 isshown having gas bladders 482 that extend the length of the tube 412.Each gas bladder is independently controlled with a regulator valvemanifold assembly 486, to optimize the stability of the system. An arrayof solar reflectors 410 can be used together, in which a subset of thetubes can be inflated with the other tubes partially or completelydeflated to control the angle at which the tubes float in the supportingbody of liquid (not shown). The assembly can incorporate similarfeatures as discussed with reference to other embodiments, including endcap assemblies 424, reflective sheet 414, gas and liquid pass-throughtubes 432, 434, a rotation assembly 426 including a motor (not shown)and a transmission system 430 and so on.

Turning to FIGS. 12-14, exemplary embodiments of a solar reflectorassembly with an externally mounted reflector will be described. Withreference now to the drawings, and particularly FIG. 12, there is showna solar reflector assembly 510 including an inflated elongated tube 512and a reflective sheet 514 coupled to an exterior wall 517 of the tube,usable as a solar reflector and/or a photobioreactor, in which the tubeis disposed on a supporting body of liquid (not shown). The reflectivesheet 514 is disposed along the top of the tube 512.

Supports 525 are disposed on an exterior side 517 of the tube 512. Thelongitudinal sides of the reflective sheet 514 are coupled to thesupports 525 and an intermediate section of the reflector sheet 514 canbe coupled to the tube 512, such that the reflective sheet 514 isgenerally flat. The elongated tube 512 has an upper portion 521 and alower ballast portion 523 containing reservoir liquid 520, though theupper and lower ballast portions are not physically separated because ofthe external location of the reflective sheet 514. In exemplaryembodiments, the elongated tube 512 is a unitary structure that includeslower ballast portion 523, which provides ballast for the solarreflector assembly 510. In other words, lower ballast portion 523 is thelower section of the elongated tube itself and, as such, is integrallyformed with the elongated tube 512. This structure is advantageousbecause it obviates the need for additional components or structuralelements to facilitate ballast. The elongated tube 512 is made of athin-gauge, flexible material, as described in more detail above, and,in contrast to other embodiments, need not be transparent because thereflective sheet 514 is externally mounted.

With reference now to FIG. 13, a second embodiment is shown in which thereflector sheet 514 is positioned and attached in a similar manner as inFIG. 12. However, the longitudinal sides 527 a, 527 b of the reflectorsheet 514 are raised relative to the intermediate section 529 of thesheet 514, such that the reflected solar radiation can be focused. Moreparticularly, the reflective sheet 514 is mounted to have a generallyv-shaped cross section. In other embodiments, the reflective sheet 514can be mounted to have various other cross-sectional shapes such asu-shaped or parabolic, among others.

In the exemplary embodiments of FIGS. 12 and 13, the supports 525 areformed as inflatable tubes similar to the primary tube 512. The supports525 are formed of a single sheet of plastic such as polyethylene, havinga thickness between about 50 microns (2 mil) and 300 microns (12 mil).In other embodiments, the supports 525 can be formed of multiple layersand multiple sections of material. In addition, other lightweight,flexible materials or combinations of materials can be used for thesupports.

The supports 525 of the exemplary embodiments are independentlyinflatable relative to each other and the primary tube 512.Alternatively, the supports 525 can be operatively coupled to each otherand/or to primary tube 512 to enable air to pass between the componentsto maintain air pressure therein.

In the exemplary embodiments of FIGS. 12 and 13, the supports 525 have agenerally circular cross section. In other embodiments, the supports 525can have other cross-sectional shapes, to facilitate other shapes forthe reflective sheet 514 such as a parabolic shape. In addition, thesupports 525 run substantially the entire length of the tube 512. Inother embodiments, multiple supports 525 can be used and can beintermittently spaced along the length of the tube 512. Moreover, thesupports 525 need not be inflatable. Rather, other structure can be usedto maintain the reflective sheet 514 in the proper position.

With reference now to FIG. 14, a rigid reflector sheet 514 is disposedtangentially along the top of the tube 512. The rigid reflector 514 issupported by its connection to the tube 512 and its rigidity. Thereflector 514 can be formed of reflective material mounted on a rigidbase sheet. In the present embodiment, the base sheet is formed of rigidpolyvinyl chloride (RPVC) having a thickness between about 200 and 300microns. Other exemplary materials that can be used includethermoplastic polymers and other materials having rigidity sufficient tomaintain a prescribed cross-sectional geometry independent of lateralsupports 525. The rigid reflector 514 can be rolled up for storage ortransport, and yet configured to remain relative flat when deployed.

An externally mounted reflector sheet can also be used in embodimentsdescribed above in which a plurality of elongated tubes are coupledtogether along longitudinal sides, forming a raft, as well as withembodiments having gas bladders that extend the length of the tube(s).

Turning to FIGS. 15 and 16, a system 5 of generating energy from solarradiation is shown, having a solar collector 92 that includes solar PVcells 94 disposed below heat-transfer pipes 96. The PV cells areconfigured to receive energy from reflected radiation within aprescribed wavelength, such as the visible light spectrum. The solarreflectors concentrate reflected radiation on the PV cells, therebyoptimizing efficiency. The heat-transfer pipes are used to passheat-transfer fluid as discussed above. Beneficially, the pipes arepositioned to absorb reflected radiation from the solar reflectors aswell as serving as a heat sink for the PV cells, cooling the PV cellsand keeping them in an optimal heat range to minimize risk ofoverheating. In an alternate embodiment, thermoelectric modules (using,e.g., the Seebek effect) could be substituted for the PV cells. Theheat-transfer fluid can capture the IR portion of the reflectedradiation, thereby collecting heat for use in a generator. Once heated,the heat-transfer fluid can be used to generate energy as known in theart, such as electricity or process heat (as discussed above). As inpreviously discussed embodiments, the solar reflector assemblies 10includes an elongated tube 12 having an upper portion 21 and a lowerballast portion 23 containing a reservoir liquid 20, a reflective sheet14, end cap assemblies 24 and rotation assembly 26. The solar reflectorassemblies 10 are supported by a body of liquid 16 in a pool 19 androtate to direct reflected solar radiation to solar collector 92.

In each of the forgoing configurations, the reflective sheet can befully reflective, such as when used for embodiments configured only as asolar reflector. Alternatively, the reflective sheet can be configuredas a hot mirror, as disclosed in the U.S. Patent Application Ser. No.61/233,667, filed Aug. 13, 2009, which is incorporated by referenceherein in its entirety, and described herein, for embodiments configuredfor biomass generation or for a combined solar reflector andphotobioreactor assembly (“CSP/PBR assembly”). It should be noted thatin exemplary embodiments employing both internal and exterior mountingof the reflective sheet, the tube material is at least partiallytranslucent such that biomass may grow in the ballast fluid in the lowerballast portion of the tube. In addition, biomass may grow in the poolsof support liquid. This biomass could be harvested and processed into auseful product

In exemplary embodiments the reservoir of liquid within the tubes canalso be used to grow biomass using systems and methods as disclosed inU.S. Patent Application Ser. No. 61/152,949, filed Feb. 16, 2009 (“'949Application”), which is incorporated by reference herein in itsentirety. With reference now to the drawings, and particularly FIGS. 17and 18, there is shown an array 601 of concentrated solarpower/photobioreactor assemblies 610 (“CSP/PBR assemblies”). EachCSP/PBR assembly 610 includes an inflated elongated tube 612 having areflective sheet 614 coupled along opposed sides of the sheet to aninterior wall 615 of the tube. Thus, the tube 612 is divided into anupper portion 621 and a lower ballast portion 623.

The reflective sheet is configured to reflect IR radiation towards asolar collector 618, while allowing visible light to pass through to aculture medium 620 within the lower ballast portion 623 of the tube 612.The array is supported by a body of liquid 616 in a pool 619.

The reflective sheet 614 is formed of lightweight flexible reflectivematerial configured to allow prescribed wavelengths of solar radiationto pass through, while reflecting other wavelengths of solar radiationtowards the solar collector 618. In exemplary embodiments, thereflective sheet is formed as a hot mirror, configured to reflect IRradiation (e.g., heat reflective) while allowing visible light to passthrough (e.g., visibly transparent), across wide angles of incidence.Thus, IR radiation is reflected towards the solar collector, while thevisible light passes through to the culture medium 620 to facilitategrowth of the biomass, e.g., algal biomass. Moreover, minimizingpenetration of IR radiation into the culture medium reduces the heatload of culture, allowing the culture to be maintained at a temperatureconducive to optimal biomass growth. It should be noted that in this andother exemplary embodiments some tubes could be deployed with hotmirrors and some with full spectrum reflectors, in order to finely tunethe percentage of insolation that makes it into culture to generatebiomass, and how much insolation is reflected to the receiver for powergeneration.

The term “visibly transparent,” unless otherwise specified, is intendedto refer to an attribute of the reflective sheet of transmitting a largefraction (e.g., an average of at least 50%) of visible radiation (e.g.,at least between about 400 nm to about 700 nm) therethrough. The term“heat reflective,” unless otherwise specified, is an attribute of thereflective sheet of reflecting a large fraction (e.g., an average of atleast 50%) of IR radiation (e.g., above 750 nm).

In exemplary embodiments, the reflective sheet 614 comprises adielectric thin film disposed on a flexible substrate, such as aflexible polymeric sheet. For example, the reflective sheet 614 caninclude flexible films such as IR reflective films sold under the brandname Prestige™ Series, available from 3M Company. The reflective sheet614 is further configured to endure a high moisture environment, withoutsignificant deterioration. The dielectric film can comprise one or morelayers (or stacks) disposed on the substrate. In multi-layerconfigurations, the thickness of each of the layers can be selected tooptimize the properties of the reflective sheet. Moreover, interveninglayers having varying properties can be used to optimize performance ofthe reflective sheet. In other embodiments, the reflective sheet cancomprise other materials, known in the art, having sufficientcharacteristics for use in the intended purposes, such as metal oxidesdisposed on a substrate. Suitable substrates can include standardcontractor-grade low-density polyethylene (LDPE), polyethyleneterephthalate (PET) (e.g., uniaxial, biaxial), polyester,polyterephthalate esters, polyethylene naphthalate, polypropylene, andothers.

In exemplary embodiments, the reflective sheet 614 is configured to bevisibly transparent and heat reflective across a wide range for theangle of incidence of solar radiation, (e.g., 0 degrees to at least 60degrees). At very high angles of incidence, the reflective sheet maybehave more like a full spectrum reflector. As discussed below, theassembly can be configured to rotate to track the sun such that thereflective sheet 614 can be optimized for operation with a tight rangefor the angle of incidence of solar radiation (e.g., ±20 degrees).

As shown in FIG. 19 a, end cap assembly 624 may include liquid transfertubes 632 and gas transfer tubes 634 that extend from the end caps.Liquid can be injected or withdrawn through liquid transfer tubes toregulate how high the elongated tubes 612 float in the support liquid616. Similarly, gas can be injected or withdrawn through gas transfertubes. The inlets and outlets pass through pipes 636, which also serveas axles on which end-caps rotate.

The end cap assembly 624 may also comprise eccentrically mountedpass-through fittings 639 instead of transfer tubes, as shown in FIG. 19b. Pass-through fittings 639 provide access to the inside of the tube612 to facilitate flow of gas and/or liquid into and out of the tubesthrough fluid lines 637.

With reference now to FIG. 20, a chart is shown, depicting thetransmission percentage across a wavelength spectrum for an exemplaryembodiment of a reflective sheet at a normal angle of incidence. In thischart, the x-axis shows wavelength in nanometers (nm), and the y-axisshows percent of incident energy reflected or transmitted. The solidline represents the percent transmission, while the dashed linerepresents the percent reflection. In this exemplary configuration, thereflective sheet is configured to allow substantial transmission ofwavelengths between about 400 nm and 700 nm and to substantially reflectwavelengths between above 750 nm. More particularly, the reflectivesheet allows transmittance of at least 50 percent of incident energy inthe wavelength band between about 400 nm and 700 nm at normal incidence.Moreover, over 80 percent of the solar radiation between 500 nm and 600nm passes through the reflective sheet to radiate the culture medium.Meanwhile, above 700 nm, the reflective sheet becomes highly reflective,even at normal incidence.

In other embodiments, the reflective sheet can be configured to variedparameters for reflection and transmission performance. For example, thereflective sheet can be configured to achieve higher levels oftransmittance within the visible spectrum, particularly withinwavelengths to optimize photosynthesis (e.g., between about 380 nm-420nm, at the lower end, and about 690 nm-750 nm, at the upper end). In yetother embodiments, the reflective sheet can be configured for hightransmission (e.g., above 50 percent) for a range (or ranges) within thevisible spectrum, such as, between about 400-500 nm and/or about 600-700nm. Such ranges can be selected based on the needs of an algal cultureof a prescribed embodiment.

The reflective sheet's performance parameters as a heat reflector canalso be varied across embodiments without departing from the disclosure.For example, it is contemplated to configure the reflective sheet tohave a high percentage of reflection for substantially all incidentsolar IR radiation above about 700 nm or, in other embodiments, aboveabout 750 nm. More particularly, the reflective sheet reflects at least50 percent of incident energy at wavelengths above about 750 nm atnormal incidence, and in some instances reflects at least 90 percent ofincident energy at wavelengths above about 750 nm at normal incidence.In yet other embodiments, the reflective sheet can be configured to havehigh percentage of reflection within a bounded range of IR wavelengths.Exemplary ranges include 700-1200 nm, 700-2000 nm, 750-1200 nm, and750-2000 nm, among others. It should be appreciated that other rangescan be used, to account for performance, location, cost, and otherconsiderations.

With reference again to FIGS. 17-19, each tube 612 is formed oftransparent, lightweight flexible plastic coupled at each end to rigidend cap assemblies 624, which facilitate the flow of liquid and gas intoand out of the tubes. More particularly, each CSP/PBR assembly 610 maycomprise an end cap assembly 624 coupled to an end of the elongated tube612, or two end cap assemblies 624, with one coupled to each end. Endcap assemblies 624 include liquid transfer tube 632 and gas transfertube 634. Liquid transfer tube 632 provides access to the culture medium620 and may facilitate addition of nutrients and harvesting of biomass.The CSP/PBR array 601 may further include a rotation assembly 626operatively connected to one or both ends of the elongated tubes 612. Inparticular, the rotation assembly may include a motor 628 coupled to endcaps 624 by a transmission system 630 to turn the tubes 612 to track thesun.

Positive pressure within the tube maintains the tube in a substantiallyrigid, cylindrical configuration. In addition to growing biomass, theculture medium within the tube facilitates ballast of the tube on thesupporting liquid 616 in pool 619. The tube will float such that the topsurface of the liquid within the tube is generally parallel with thesurface of liquid on which the tube is floating. The level of liquidwithin the tube can vary, from empty to fully filled with liquid, asdesired. The system may be further configured to extract biomass fromwithin the CSP/PBR assemblies for processing. Various approaches can beused for this purpose. For example, the present inventor's co-pending‘949 application, entitled “System for Concentrating Biological Cultureand Circulating Biological Culture and Process Fluid,” which isincorporated by reference herein for all purposes, discloses effectiveapproaches towards that end.

It should be noted that any of the above-described solar reflectorassembly and system embodiments could be modified to incorporate aculture medium to provide different embodiments of a CSP/PBR assembly.For instance, the elongated tube of the CSP/PBR assembly can beconfigured to achieve various different cross-sectional shapes, asdepicted in FIGS. 9 a-b with reference to the solar reflector assembly.A CSP/PBR assembly could also have gas bladders to optimize thestability of the system, like the solar reflector assembly depicted inFIGS. 10-11.

In addition, as with the solar reflector assemblies discussed above withreference to FIGS. 1 and 2, the system can include an array of CSP/PBRassemblies configured to reflect solar radiation towards multiple solarcollectors. For example, the system can include groupings of CSP/PBRassemblies disposed on opposing sides of linear solar collectors, andthe CSP/PBR assemblies can be directed to the closest solar collector.As with the solar reflector assemblies discussed above with reference toFIGS. 2, 4 and 5, an array of CSP/PBR assemblies can be configured torotate to track the sun to ensure that the reflective solar radiation isdirected towards the reservoir. Systems of generating energy from solarradiation including PV cells, such as those discussed above withreference to FIGS. 15 and 16, could also incorporate a culture mediumfor growing biomass to provide CSP/PBR assemblies. As discussed above,such CSP/PBR systems optimize efficiency by reflecting radiation on thePV cells, and heat-transfer pipes both absorb radiation and serve as aheat sink for the PV cell. Thermo-electric modules employing, e.g., theSeebek effect could also be used, as discussed above.

Turning to FIGS. 21-26, exemplary embodiments of a solar reflectorassembly having additional shapes and cross-sections are illustrated.FIG. 21 shows an embodiment of a solar reflector assembly 710 comprisingan elongated flexible tube 712 having an upper portion 721, a lowerballast portion 723 and an “egg shaped” cross section. The tube 712contains ballast liquid 720 and sits on an expanse of liquid 716. Thisconfiguration is made by coupling the reflective panel or sheet 714 tothe inner walls 715 of the tube 712 in two places that would normallyform a chord of the circular cross section of a certain length. Thereflective sheet 714, however, is slightly shorter than thecharacteristic chord length, thus pulling in the sides of the circles atthe attachment points A. In the case of modest internal pressure that isequal on both sides of the panel, this advantageously guarantees thatthe panel is flat, even in the case of modest irregularities introducedin manufacturing. The lower ballast portion 723 remains largely (but notexactly) cylindrical, and the upper portion's protruding “egg” shapeddome 735 does not materially impact the performance of the system. Itshould be noted in this regard that various exaggerated geometries arepossible, with very large egg domes having no adverse impact onperformance.

FIGS. 22-23 illustrate exemplary embodiments of solar reflectorassemblies 810 with each assembly comprising an elongated flexible tube812 having an upper portion 821, lower ballast portions 823 a, 823 b anda “triple panel” cross section. This configuration is made by attachinga second sheet or panel 845 to the reflective sheet or panel 814 eitherin the middle B or at some other point between the two ends of thereflective sheet 814 and connecting the bottom of the second panel 845to the bottom of the tube 812 at some middle point C or at some otherpoint. This allows the reflective sheet 814 to be pulled into a “V”formation. There are other ways to create a “V” formation, for example,with a weight attached at the middle of reflective sheet 814. The “V”formation provides the advantage of a tighter focus on the target. Thetube 812 contains ballast liquid 820 and sits on an expanse of liquid816.

The “triple panel” solar reflector assemblies can be arranged in anarray configuration, as shown in FIG. 23. This view shows that there areholes 847 defined in the second panel 845. This facilitates the passageof liquid between the two lower ballast portions 823 a, 823 b created bythe second panel 845. Holes 847 facilitate the equalization of the levelof ballast within the tube during rotation.

FIG. 24 illustrates an array of CSP/PBR assemblies 910 having atriple-panel configuration. Each CSP/PBR assembly includes an inflatedelongated tube 912 having a reflective sheet 914 coupled along opposedsides of the sheet to an interior wall 915 of the tube. A second sheetor panel 945 is attached to the reflective sheet or panel 914 either inthe middle or at some other point between the two ends of the reflectivesheet 914 and connecting the bottom of the second panel 945 to thebottom of the tube 912 at some point in the middle or at some otherpoint. Thus, the tube 912 is divided into an upper portion 921 and twolower ballast portions 923 a, 923 b. The reflective sheet is configuredto reflect IR radiation towards a solar collector (not shown), whileallowing visible light to pass through to a culture medium 920 withinthe lower ballast portions 923 a, 923 b of the tube 912. The array issupported by a body of liquid 916 in a pool 919. Holes 947 defined inthe second panel 945 facilitate the equalization of the level of ballastwithin the tube during rotation.

Turning to FIGS. 25-26, an embodiment of a solar reflector assemblyhaving an “Egg shaped, triple panel” cross section will be described.Each solar reflector assembly 1010 comprises an elongated flexible tube1012 having an upper portion 1021, lower ballast portions 1023 a, 1023 band an “egg shaped, triple panel” cross section. This configuration ismade by attaching a second sheet or panel 1045 to the reflective sheetor panel 1014 either at a middle point B or at some other point betweenthe two ends of the reflective sheet 1014 and connecting the bottom ofthe second panel 1045 to the bottom of the tube 1012 at some middlepoint C or at some other point. This allows the reflective sheet 1014 tobe pulled into a “V” formation. The second panel 1045, is shorter thanotherwise necessary which leads to the deformation at C. Laying thisreflector assembly on an expanse of liquid 1016 and using internalballast provides a stable, level reflector array that is easily turnedby actuators at each end.

The reflective sheet 1014 is slightly shorter than the characteristicchord length, thus pulling in the sides of the circles at the attachmentpoints A. In the case of modest internal pressure that is equal on bothsides of the panel, this advantageously guarantees that the panel isflat, even in the case of modest irregularities introduced inmanufacturing. The lower ballast portions 1023 a, 1023 b together remainlargely cylindrical. Holes 1047 defined in the second panel 1045facilitate the equalization of the level of ballast within the tubeduring rotation. As shown in FIG. 26, the “egg shaped, triple panel”solar reflector assemblies can be arranged in an array configuration.The array of solar reflector assemblies is supported by a body of liquid1016 in a pool 1019.

FIGS. 27 a-27 b illustrate further exemplary embodiments of solarreflector assemblies having simplified end designs. FIG. 27 a shows anembodiment of a solar reflector assembly utilizing direct coupling to arotation axle. Solar reflector assembly 1110 comprises an elongatedflexible tube 1112 having an upper portion 1121 and a lower ballastportion 1123. The elongated tube 1112 is directly coupled to a rotationaxle 1136 without an end cap component. It can be seen that the tube1112 develops folds 1157 where it is bunched up and locked onto the axle1136. A retaining ring 1153 facilitates locking of the tube 1112 ontothe axle 1136. Axle 1136 includes liquid transfer tube 1132 and gastransfer tube 1134. The axle 1136 may also be coupled to a transmissionsystem 1130 that serves to turn the tube 1112 to track the sun.

FIG. 27 b shows an embodiment of a solar reflector assembly without anend cap or a rotation axle, but instead is heat-sealed at its ends andemploys pass-through fittings for ingress and egress of fluids. Solarreflector assembly 1110 comprises an elongated flexible tube 1112 havingan upper portion 1121 and a lower ballast portion 1123. In thisexemplary embodiment, solar reflector assembly 1110 employs a heat-seal1159 at the end. Pass-through fittings 1139 provide access to the insideof the tube 1112 to facilitate flow of gas and/or liquid into and out ofthe tubes through fluid lines 1137.

Rotation of the tube 1112 is accomplished by a rotation assembly thatincludes a strap 1149 and a stabilizer 1151. In this embodiment, thestrap is coupled to the tube 1112 by being wrapped 1147 around the tube,but other means of coupling a rotation assembly to the tube arepossible. The tube 1112 is rotated by pulling the strap 1149 in thedirection corresponding to the desired turning direction for the tube1112. Stabilizer 1151 with stabilizer rods 1143 prevents lateralmovement of the tube when strap 1149 is pulled, thereby inducingrotation as opposed to translation. It will be appreciated that arotation assembly can be placed anywhere along the length of the tube,and that multiple different means, including end-caps, axles, straps andother means can be employed simultaneously to impart rotation on thetube.

It should be noted that exemplary embodiments described herein can becontrolled by a computer. Either an open loop system that ispre-programmed with the position of the sun in the sky or a closed loopsystem that has a sensor or sensors that detect the position of the sunin the sky or a combination of these two strategies can be used tocontrol the position of the tubes.

Thus, it is seen that systems and methods of generating energy fromsolar radiation are provided. It should be understood that any of theforegoing configurations and specialized components or chemicalcompounds may be interchangeably used with any of the systems of thepreceding embodiments. Although exemplary embodiments of the presentdisclosure are described hereinabove, it will be evident to one skilledin the art that various changes and modifications may be made thereinwithout departing from the disclosure. It is intended in the appendedclaims to cover all such changes and modifications that fall within thetrue spirit and scope of the disclosure.

1. A solar reflector assembly comprising: a primary inflatable elongatedtube having an upper portion formed at least partially of flexiblematerial and a lower ballast portion formed at least partially offlexible material; and a reflective sheet coupled to an exterior wall ofthe upper portion of the primary tube to reflect solar radiation;wherein the primary tube has an axis of rotation oriented generallyparallel to a surface of a supporting body of liquid.
 2. The solarreflector assembly of claim 1 wherein the lower ballast portion definesa reservoir containing liquid facilitating ballast, the liquid having atop surface generally parallel to the surface of the supporting body ofliquid.
 3. The solar reflector assembly of claim 1 further comprising atleast one support component disposed on the exterior wall of the primarytube to support the reflective sheet.
 4. The solar reflector assembly ofclaim 3 wherein pressure from air inside the primary tube compresses thesupport component such that the reflective sheet maintains asubstantially rigid configuration.
 5. The solar reflector assembly ofclaim 3 wherein the at least one support component has a generallycircular cross section.
 6. The solar reflector assembly of claim 1wherein the at least one support component is a secondary inflatabletube.
 7. The solar reflector assembly of claim 6 wherein the at leastone support component includes two support components.
 8. The solarreflector assembly of claim 7 wherein the two support components areindependently inflatable.
 9. The solar reflector assembly of claim 7wherein the two support components are operatively coupled to each otherto enable air to pass between the two support components.
 10. The solarreflector assembly of claim 6 wherein the at least one support componentis operatively coupled to the primary tube to enable air to pass betweenthe primary and secondary inflatable tubes.
 11. The solar reflectorassembly of claim 1 wherein the primary tube further comprises a culturemedium for photosynthetic biomass.
 13. The solar reflector assembly ofclaim 3 wherein the at least one support component runs substantiallythe entire length of the primary tube.
 14. The solar reflector assemblyof claim 1 further comprising a solar collector spaced apart from theprimary tube and positioned to receive reflected solar radiation fromthe reflective sheet.
 15. The solar reflector assembly of claim 1wherein the reflective sheet substantially reflects a first prescribedwavelength range and substantially transmits a second prescribedwavelength range therethrough.
 16. A system for generating energy fromsolar radiation, comprising: a pool housing a supporting body of liquid;one or more solar reflector assemblies floating on the supporting bodyof liquid, each solar reflector assembly including: a primary inflatableelongated tube having an upper portion at least partially formed offlexible material and a lower ballast portion at least partially formedof flexible material, and an axis of rotation oriented generallyparallel to a surface of the supporting body of liquid; and a reflectivesheet coupled to an exterior wall of the upper portion of the primarytube to reflect solar radiation; and a solar collector spaced apart fromthe primary tube and positioned to receive reflected solar radiationfrom the reflective sheet; wherein the lower ballast portion of theprimary tube contains liquid facilitating ballast, the liquid having atop surface generally parallel to the surface of the supporting body ofliquid.
 17. The system of claim 16 further comprising at least onesupport component disposed on the exterior wall of the primary tube tosupport the reflective sheet.
 18. The system of claim 17 whereinpressure from air inside the primary tube compresses the supportcomponent such that the reflective sheet maintains a substantially rigidconfiguration.
 19. The system of claim 16 wherein the at least onesupport component is a secondary inflatable tube.
 20. The system ofclaim 16 wherein the primary tube further comprises a culture medium forphotosynthetic biomass.